The WHO Africa office said the quick progression from sickness to death in Boloko is a key concern, along with the high number of deaths in Bomate. Congo’s Ministry of Health said about 80% of the patients share similar symptoms including fever, chills, body aches and diarrhea.

The outbreak has been traced, tentatively, to three children who ate a bat, the W.H.O. said, and known threats like Ebola and Marburg have been ruled out.